The increased exposure of composite materials to a wide range of environmental conditions has increased the demands placed on these materials. One such demand involves the deicing of composite structures. For example, the formation of ice on structures such as on leading edges of aircraft aerodynamic surfaces, such as wings, empennages or engine nacelles poses significant technical and safety concerns. A layer of ice as thin as one (1) millimeter (mm) may be sufficient to destabilize an in-flight aircraft.
It has been indicated that to prevent against the formation of ice or to eliminate ice already formed, the leading edge of such aerodynamic surfaces can be deiced by warming with pressurized hot air tapped off from at least one of the engines of the aircraft and conveyed into the interior of the leading edge by a pressurized hot air circulation circuit. The hot air operates to weaken the ice-surface bonding which destabilizes the ice, thereby causing the slipstream behind the aircraft to dislodge the ice from the surface (e.g. a wing) and facilitate its removal.
Another approach to deicing includes a heating coil disposed beneath a surface which is prone to accumulate ice. However, use of embedded heating elements requires that heat generated by the heating elements be effectively conducted to the surface of the structure to melt the ice. In this regard, it can be difficult to heat a composite external surface effectively due to poor heat transfer from imbedded heating devices to the surrounding composite material. Although the use of composite materials for structures such as aircraft wings is desirable for their favorable strength to weight ratios, such materials are generally insulators due to the presence of the matrix, such as a typical resin matrix. Thus, resistive heating has been limited due poor conducting properties of the composite materials.
Another approach to providing resistive heating is to apply a metal spray coating over a surface of the composite structure. An electric current is applied to the metal coating, which provides resistive heating to dislodge any ice deposited thereon. However, such metal coatings incur increased cost and complexity due to the specialized manufacturing processes used to apply the coatings. Moreover, the increased weight of the overall structure detracts from the advantage of provided by a composite structure. Finally, such metal coatings are susceptible to galvanic corrosion making them susceptible to structural failures after repeated use.
It would be beneficial to develop new composite structures for applications that require deicing. The present invention satisfies this need and provides related benefits as well.